The invention relates to an interconnect arrangement and to a method for fabricating an interconnect arrangement.
Integrated circuit arrangements are being produced with an ever greater packing density. The result of this is that interconnects in metallization layers are at an ever decreasing spacing from one another. As a result, capacitances which are formed between the interconnects rise and lead to high signal propagation times, high power losses and crosstalk. Hitherto, SiO2, the relative dielectric constant of which is εr=3.9, has primarily been used as the dielectric for providing insulation between the interconnects.
There are a number of known methods for reducing the relative dielectric constant ∈r and therefore for reducing the capacitance between interconnects within an interconnect layer, for example from J. G. Fleming et al.: “Lowering of Intralevel Capacitance Using Air Gap Structures”, Conference Proceedings ULSI XII, Materials Research Society, pp. 471–477, 1997; T. Ueda et al.: “A Novel Air Gap Integration Scheme for Multi-level Interconnects using Self-aligned Via Plugs”, IEEE Proc. 1998 Symp. VLSI Techn. Digest of Technical Papers, pp. 46–47, 1998; B. Shieh et al.: “Integration and Reliability Issues for Low Capacitance Air-Gap Interconnect Structure”, IEEE Proc. 1998 IITC, pp. 125–127, 1998; B. Shieh et al.: “Air-Gap Formation During IMD Deposition to Lower Interconnect Capacitance”, IEEE Electron Device Letters, Vol. 19, No. 1, pp. 16–18, 1998; B. Shieh et al.: “Air gaps lower k of interconnect dielectrics”, Solid State Technology, pp. 51–58, February 1999; T. Ueda et al.: “Integration of 3 Level Air Gap Interconnect for Sub-quarter Micron CMOS”, IEEE Proc. 1999 Symp. VLSI Techn. Digest of Technical Papers, 1999; V. Arnal et al.: “Integration of a 3 Level Cu—SiO2 Air Gap Interconnect for Sub 0.1 micron CMOS Technologies”, IEEE Proc. 2001 IITC, 2001; and V. Arnal et al.: “A Novel SiO2-Air Gap Low K for Copper Dual Damascene Interconnect”, Conference Proceedings ULSI XVI, Materials Research Society, pp. 71–76, 2001.
According to the prior art, cavities are produced between the interconnects within an interconnect layer. The insulating dielectric, which determines the capacitance between the interconnects, therefore has a relative dielectric constant ∈r which is almost equal to 1. For insulation purposes, the interconnects themselves are enclosed at the top and bottom by solid SiO2 layers.
Since the capacitances of the insulating layers above and below also make a not insignificant contribution to the overall capacitance between interconnects which adjoin one another within a layer, and these insulating layers still consist of solid SiO2 material, the high relative dielectric constant ∈r of these insulating layers has a considerable influence onto the overall capacitance between the adjacent interconnects.